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Abstract:

A mask frame assembly using a plurality of stick-shaped split masks. The
mask frame assembly includes a plurality of split masks, each of which
includes a deposition pattern corresponding to a unit screen. Each of the
split masks is formed of a plurality of partial masks to form the
deposition pattern corresponding to a unit screen. Accordingly, the split
masks accommodating a pattern corresponding to a large screen may be
easily manufactured without an increase in the amount of etching errors.

Claims:

1. A mask frame assembly for deposition of thin films, the mask frame
assembly comprising: a frame comprising an opening portion therein; and a
plurality of split masks, each of which comprises a deposition pattern
corresponding to a unit screen, wherein two end portions of each of the
plurality of split masks are fixed to the frame and the deposition
pattern is located in the opening portion, wherein each of the plurality
of split masks comprising a plurality of partial masks coupled to form
the deposition pattern corresponding to the unit screen.

2. The mask frame assembly of claim 1, wherein the plurality of partial
masks comprise a first partial mask comprising a first partial pattern of
the deposition pattern and a second partial mask comprising a second
partial pattern of the deposition pattern, and wherein sides of the first
and second partial masks opposing each other are bonded to each other
using an adhesive so as to bond the first and second partial masks.

3. The mask frame assembly of claim 2, wherein the first partial pattern
and the second partial pattern have a uniform pattern pitch throughout
the deposition pattern including a bonding portion of the first partial
mask and the second partial mask.

4. The mask frame assembly of claim 3, wherein the adhesive is a
UV-curing adhesive.

5. The mask frame assembly of claim 4, wherein the UV-curing adhesive is
coated on upper and lower surfaces of the bonding portion.

6. The mask frame assembly of claim 5, wherein the sides of the first
partial mask and the second partial mask which form the bonding portion
of the first and second partial masks are substantially parallel to each
other.

7. The mask frame assembly of claim 3, wherein the adhesive is a
thermosetting adhesive.

8. The mask frame assembly of claim 7, wherein the thermosetting adhesive
is coated on the sides of the bonding portion.

9. The mask frame assembly of claim 8, wherein the sides of the first
partial mask and the second partial mask are substantially parallel to
each other.

10. A method of manufacturing a mask frame assembly for deposition of
thin films, the method comprising: providing a plurality of partial masks
comprising partial patterns, each of the partial patterns comprising a
portion of a deposition pattern corresponding to a unit screen;
manufacturing a split mask by coupling the partial masks such that the
partial patterns form the deposition pattern corresponding to the unit
screen; and fixing the split mask to a frame.

11. The method of claim 10, wherein the partial masks comprise a first
partial mask having a first partial pattern and a second partial mask
having a second partial pattern, wherein the first partial pattern and
the second partial pattern have a uniform pattern pitch throughout the
deposition pattern including a bonding portion of the first partial mask
and the second partial mask.

12. The method of claim 11, wherein the manufacturing of the split mask
comprises: arranging the first partial mask and the second partial mask
such that sides of the first partial mask and the second partial mask are
located adjacent to each other with a predetermined distance; applying a
UV-curing adhesive to the sides of the first and second partial masks;
and curing the UV-curing adhesive by UV irradiation.

13. The method of claim 12, wherein the applying and curing of the
UV-curing adhesive comprises: applying the UV-curing adhesive on an upper
surface of the bonding portion of the first partial mask and the second
partial mask and curing the UV-curing adhesive; and applying the
UV-curing adhesive on a lower surface of the bonding portion of the first
partial mask and the second partial mask and curing the UV-curing
adhesive.

14. The method of claim 13, wherein in the applying of the UV-curing
adhesive, a vision camera traces the sides of the first partial mask and
the second partial mask to be bonded, and an applying apparatus follows
the vision camera to apply the UV-curing adhesive.

15. The method of claim 11, wherein the manufacturing of the split mask
comprises: applying a thermosetting adhesive on sides of the first
partial mask and the second partial mask that are to be bonded to each
other; adhering the sides of the first and second partial masks with the
applied thermosetting adhesive; and heating the thermosetting adhesive
using a heater to cure the thermosetting adhesive.

16. The method of claim 15, wherein the curing of the thermosetting
adhesive comprises: curing the thermosetting adhesive by heating a first
surface of the bonding portion of the first partial mask and the second
partial mask; and curing the thermosetting adhesive by heating a second
surface of the bonding portion of the first partial mask and the second
partial mask.

17. The method of claim 15, wherein the curing of the thermosetting
adhesive comprises curing the thermosetting adhesive by heating first and
second surfaces of the bonding portion of the first partial mask and the
second partial mask at the same time.

18. The method of claim 15, wherein the heating unit comprises one of a
heating roller that rolls while touching the bonding portion to heat the
thermosetting adhesive and a blower that blows hot air toward the
thermosetting adhesive while not touching the bonding portion.

Description:

CROSS-REFERENCE TO RELATED PATENT APPLICATION

[0001] This application claims the benefit of Korean Patent Application
No. 10-2010-0127858, filed on Dec. 14, 2010, in the Korean Intellectual
Property Office, the disclosure of which is incorporated herein in its
entirety by reference.

BACKGROUND

[0002] 1. Field

[0003] The present disclosure relates to mask frame assemblies for
deposition of thin films, and more particularly, to mask frame assemblies
using split masks, and methods of manufacturing the mask frame
assemblies.

[0006] Organic light-emitting display devices realize colors based on the
principle that holes and electrons injected from an anode and a cathode
recombine in an emissive layer and emit light. Thus, organic
light-emitting display devices have a stacked structure in which the
emissive layer is inserted between the anode and the cathode. However, it
is difficult to achieve high emission efficiency using this structure,
and thus intermediate layers such as an electron injection layer, an
electron transport layer, a hole transport layer, and a hole injection
layer are selectively inserted between the electrodes and the emissive
layer.

[0007] The electrodes and the intermediate layers such as the emissive
layer of the organic light-emitting display devices may be formed using
various methods, and one of these is a deposition method. In order to
manufacture an organic light-emitting display device using a deposition
method, a fine metal mask (FMM) having the same pattern as a pattern of a
thin film that is to be formed on a substrate is aligned on the
substrate, and a material used to form the thin films is deposited to
form a thin film having a desired pattern.

[0008] However, if the FMM becomes too large, etching errors also increase
during forming patterns. Thus, split masks are used. The split masks are
formed of a various number of stick-shaped masks and attached to a frame.
That is, a mask device for use in depositing a plurality of screens of
organic light-emitting display devices on a mother substrate is used,
whereas since it is difficult to cover the entire surface of the mother
substrate using a single mask without any etching errors, several split
masks in the form of sticks having a predetermined width are attached to
the frame to form the mask device.

[0009] Recently, the screens of the organic light-emitting display devices
become large, and the size of a unit screen to be deposited become larger
than a single split mask. That is, a maximum width of a split mask which
would be able to avoid an etching error is about 150 mm and deposition
patterns corresponding to screens having 7 inches or smaller size may be
formed using this split mask. However, to accommodate a deposition
pattern corresponding, for example, to a 14-inch screen, the split mask
needs to have a width of about 300 mm. When forming a split mask having a
width of 300 mm or greater, etching errors increase.

[0010] The foregoing discussion in the background section is to provide
general background information, and does not constitute an admission of
prior art.

SUMMARY

[0011] One or more embodiments of the present invention provide mask frame
assemblies capable of easily accommodating deposition patterns
corresponding to large-surface screens without increasing etching errors
when manufacturing split masks, and methods of manufacturing the mask
frame assemblies.

[0012] According to an aspect of the present invention, there is provided
a mask frame assembly for deposition of thin films, the mask frame
assembly comprising: a frame having an opening portion therein; and a
plurality of split masks each including a deposition pattern
corresponding to a unit screen, wherein two end portions of each of the
plurality of split masks are fixed to the frame and the deposition
pattern is located in the opening portion, wherein each of the plurality
of split masks comprises a plurality of partial masks coupled to form the
deposition pattern corresponding to the unit screen.

[0013] The plurality of partial masks may comprise a first partial mask
comprising a first partial pattern of the deposition pattern and a second
partial mask comprising a second partial pattern of the deposition
pattern, and sides of the first and second partial masks opposing each
other are bonded to each other using an adhesive so as to bond the first
and second partial masks.

[0014] The first partial pattern and the second partial pattern may have a
uniform pattern pitch throughout the deposition pattern including a
bonding portion of the first partial mask and the second partial mask.

[0015] The adhesive may be a UV-curing adhesive.

[0016] The UV-curing adhesive may be coated on upper and lower surfaces of
the bonding portion and cured.

[0017] The sides of the bonding portions of the first partial mask and the
second partial mask which form the bonding portion of the first and
second partial masks may be parallel to each other.

[0018] The adhesive may be a thermosetting adhesive.

[0019] The thermosetting adhesive may be coated on sides of the bonding
portion and cured.

[0020] The sides of the first partial mask and the second partial mask may
be parallel to each other.

[0021] According to another aspect of the present invention, there is
provided a method of manufacturing a mask frame assembly for deposition
of thin films, the method comprising: providing a plurality of partial
masks including partial patterns each of which comprises a portion of a
deposition pattern corresponding to a unit screen; manufacturing a split
mask by coupling the partial masks such that the partial patterns are
connected to each other so as to form a deposition pattern corresponding
to the unit screen; and fixing the split mask to a frame.

[0022] The partial masks may comprise a first partial mask having a first
partial pattern and a second partial mask having a second partial
pattern, wherein the first partial pattern and the second partial pattern
have a uniform pattern pitch throughout the deposition pattern including
a bonding portion of the first partial mask and the second partial mask.

[0023] The manufacturing of the split mask may comprise: arranging the
first partial mask and the second partial mask such that sides of the
first and second partial masks are located adjacent to each other with a
predetermined distance; applying a UV-curing adhesive to the sides of the
first and second partial masks; and curing the UV-curing adhesive by UV
irradiation.

[0024] The applying and curing of the UV-curing adhesive may comprise:
applying the UV-curing adhesive on an upper surface of the bonding
portion of the first partial mask and the second partial mask and curing
the UV-curing adhesive; and applying the UV-curing adhesive on a lower
surface of the bonding portion of the first partial mask and the second
partial mask and curing the UV-curing adhesive.

[0025] In the applying of the UV-curing adhesive, a vision camera may
guide the coating by tracing the bonding portion of the first partial
mask and the second partial mask, and an applying apparatus may follow
the vision camera to apply the UV-curing adhesive.

[0026] The manufacturing of the split mask may comprise: applying a
thermosetting adhesive on sides of the first partial mask and the second
partial mask that are to be bonded to each other; adhering the sides of
the first and second partial masks with the thermosetting adhesive to
each other; and heating the thermosetting adhesive using a heating unit
to cure the thermosetting adhesive.

[0027] The curing of the thermosetting adhesive may comprise: curing the
thermosetting adhesive by heating a first surface of the bonding portion
of the first partial mask and the second partial mask; and curing the
thermosetting adhesive by heating a second surface of the bonding portion
of the first partial mask and the second partial mask.

[0028] The curing of the thermosetting adhesive may comprise curing the
thermosetting adhesive by heating first and second surfaces of the
bonding portion of the first partial mask and the second partial mask at
the same time.

[0029] The heating unit may comprise one of a heating roller that rotates
in contact with the bonding portion to heat the thermosetting adhesive
and a blower that blows hot air onto the thermosetting adhesive while not
touching the bonding portion.

[0030] According to mask frame assemblies and the methods of manufacturing
the mask frame assemblies, split masks accommodating patterns
corresponding to large-surface screens may be easily manufactured without
an increase in the amount of etching errors.

BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The above and other features and advantages of the present
invention will become more apparent by describing in embodiments thereof
with reference to the attached drawings in which:

[0032] FIG. 1 is a separate perspective view of a mask frame assembly
according to an embodiment of the present invention;

[0033] FIG. 2A is a schematic view illustrating a split mask of the mask
frame assembly of FIG. 1, according to an embodiment of the present
invention;

[0034]FIG. 2B is an expanded view of a concave portion of the split mask
illustrated in FIG. 2A;

[0035] FIGS. 3A through 3H are schematic views sequentially illustrating a
method of manufacturing the mask frame assembly illustrated in FIG. 1,
according to an embodiment of the present invention; and

[0036] FIGS. 4A through 4H are schematic views sequentially illustrating a
method of manufacturing the mask frame assembly illustrated in FIG. 1,
according to another embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS

[0037] Embodiments of the present invention will now be described more
fully with reference to the accompanying drawings, in which embodiments
of the invention are shown.

[0038] FIG. 1 is a separate perspective view of a mask frame assembly 100
according to an embodiment of the present invention.

[0039] Referring to FIG. 1, the mask frame assembly 10 includes a frame
120 having an opening portion 121, and a plurality of split masks 110
each of which having two end portions that are fixed to the frame 120. In
FIG. 1, only four split masks 110 are illustrated to show the opening
portion 121 for convenience of description, but when manufacturing is
completed, the opening portion 121 is completely filled with the split
masks 110.

[0040] First, the frame 120 is an outer frame of the mask frame assembly
100 and has the rectangular shape having the opening portion 121 at its
center. The two end portions of each of the split masks 110 are fixed to
a pair of opposite sides of the frame 120 by welding.

[0041] The split masks 110 are in the form of long sticks and each include
deposition patterns 111 which are to be located within the opening
portion 121, and the two end portions of each of the split masks 110 are
welded to the frame 120 as described above. The split masks 110 are
separately attached to the frame 120 in order to reduce etching errors as
described above, instead of forming one large mask covering the opening
portion 121 at once. The split masks 110 may be formed of, for example,
nickel, a nickel alloy, a nickel-cobalt alloy or the like.

[0042] FIG. 2A is a schematic view illustrating the split masks 110 of the
mask frame assembly 100 of FIG. 1, according to an embodiment of the
present invention. As illustrated in FIG. 2A, the split masks 110 are not
single bodies but are formed of a plurality of partial masks 110a and
110b that are coupled to each other. That is, adjacent sides of a first
partial mask 110a having a first partial pattern 111a and a second
partial mask 110b having a second partial pattern 111b are bonded to each
other so as to form one split mask 110. The first partial pattern 111a
and the second partial pattern 111b are connected to each other, thereby
forming a deposition pattern 111 corresponding to a unit screen. In FIG.
2A, the two partial masks 110a and 110b form one split mask 110 but the
split mask 110 may also be formed of two or more partial masks.

[0043]FIG. 2B is an expanded view of a concave portion of the split mask
illustrated in FIG. 2A. Here, predetermined pattern pitches P1, P2, and
P3 of the first and second partial masks 110a and 110b are formed
uniformly (P1=P2=P3), but a bonding portion of the first and second
partial masks 110a and 110b is included as the pattern pitch P2. That is,
the pattern pitch P1 of the first partial pattern 111a constituting the
deposition pattern 111 and the pattern pitch P3 of the second partial
pattern 111b are the same, and the pattern pitch P2 corresponding to the
bonding portion of the first and second partial masks 110a and 110b is
the same as each of the pattern pitches P1 and P3. Thus, although the
split mask 110 is formed by bonding the two first and second partial
masks 110a and 110b to each other, the pattern pitches P1, P2, and P3
within one deposition pattern 111 are uniform overall.

[0044] When forming the split mask 110 by bonding a plurality of partial
masks as the first and second partial masks 110a and 110b, the deposition
pattern 111 corresponding to a large unit screen may be easily
implemented. In addition, since the first and second partial patterns
111a and 111b are first formed in narrow portions of the first and second
partial masks 110a and 110b by etching, etching errors, which may be
generated when etching a wide member adjusted to a large screen, may be
reduced.

[0045] Hereinafter, a method of manufacturing the split mask 110 by
bonding the first and second partial masks 110a and 110b will be
described.

[0046] FIGS. 3A through 3H are schematic views sequentially illustrating a
method of manufacturing the mask frame assembly 100 illustrated in FIG.
1, according to an embodiment of the present invention. Referring to
FIGS. 3A through 3H, the first and second partial masks 110a and 110b are
bonded to each other using a UV-curing adhesive 301.

[0047] First, referring to FIG. 3A, the first and second masks 110a and
110b are aligned in such a manner that their adjacent sides face each
other in parallel, with a gap d of about 10 to 20 μm therebetween.
Later, a portion of the UV-curing adhesive 301 soaks into the gap d.

[0048] The first and second masks 110a and 110b are aligned using a vision
camera 200 as illustrated in FIG. 3A. For example, a reference pattern
glass may be disposed under the first and second partial masks 110a and
110b, and the vision camera 200 may be used to observe and determine
whether a reference pattern and the positions of the first and second
masks 110a and 110b correspond to each other so as to align the first and
second masks 110a and 110b.

[0049] Next, when the alignment of the first and second partial masks 110a
and 110b is completed, an applying apparatus 300 is started and operates
as illustrated in FIG. 3B by applying UV-curing adhesive 301 to an upper
surface of a bonding portion of the first and second partial masks 110a
and 110b.

[0050] Then a portion of the UV-curing adhesive 301 soaks into the gap d
as shown in FIG. 3c. When applying the UV-curing adhesive 301, the vision
camera 200 may trace a line of the bonding portion to guide the applying
apparatus 300, and the applying apparatus 300 may apply the adhesive to
the bonding portion while following the vision camera 200.

[0051] Then, in this state, when a UV ray 401 is irradiated to the bonding
portion using a UV irradiation apparatus 400 as illustrated in FIG. 3E,
the UV-curing adhesive 301 is cured to obtain a rigid bonding state. The
UV ray 401 may be irradiated using the UV irradiation apparatus 400 onto
the entire bonding portion or may be irradiated along the line of the
bonding portion like the applying apparatus 300 does.

[0052] The UV-curing adhesive 301 may contain a reactive oligomer, a
reactive diluent, an additive, or a photo-initiator. The reactive
oligomer may contain a modified acrylic oligomer such as epoxy,
polyester, or urethane. The reactive diluent may be an acrylic monomer,
and examples of the additive may include an adhesive additive, a filler,
an inhibitor, a thermosetting catalyst, an anaerobic catalyst, and a
colorant.

[0053] After applying the upper surface of the first and second partial
masks 110a and 110b with the UV-curing adhesive 301 in the
above-described manner, the first and second partial masks 110a and 110b
may be reversed to apply a lower surface of the first and second partial
masks 110a with the UV-curing adhesive 301 and cure the same. When
reversing the first and second partial masks 110a and 110b, instead of
reversing just the first and second partial masks 110a and 110b, a jig
(not shown) supporting the first and second partial masks 110a and 110b
may also be reversed at the same time so that the previously cured
UV-curing adhesive 301 does not tear off.

[0054] Then the lower surface of the first and second partial masks 110a
and 110b is applied with the UV-curing adhesive 301 using the applying
apparatus 300 as illustrated in FIG. 3F, and then a UV ray 401 is
irradiated onto the lower surface of the first and second partial masks
110a and 110b by using the UV irradiation apparatus 400 as illustrated in
FIG. 3G to cure the UV-curing adhesive 301.

[0055] Accordingly, the UV-curing adhesive 301 on both the upper and lower
surfaces of the UV-curing adhesive 301 is cured to be in a rigid bonding
state, and the split mask 110 including the deposition pattern 111
corresponding to a large unit surface screen is manufactured.

[0056] The split masks 110 manufactured in this manner are attached to the
frame 120 to form the mask frame assembly 100, as described above with
reference to FIG. 1.

[0057] The adjacent sides of the first and second partial masks 110a and
110b may be inclined at a predetermined angle while being parallel to
each other as illustrated in FIG. 3H. In this case, the split masks 110
may also be manufactured by applying and curing the UV-curing adhesive
301 on upper and lower surfaces of a bonding portion using the same
process as illustrated in FIGS. 3A through 3G.

[0058] Accordingly, the split masks 110 that include the deposition
pattern 111 corresponding to a large screen may be easily manufactured in
the above-described operations without an increase in the amount of
etching errors.

[0059] FIGS. 4A through 4H are schematic views sequentially illustrating a
method of manufacturing the mask frame assembly illustrated in FIG. 1,
according to another embodiment of the present invention.

[0060] Hereinafter, a method of manufacturing a split mask 110 by bonding
first and second partial masks 110a and 110b by using a thermosetting
adhesive 501 will be described with reference to FIGS. 4A through 4H.

[0061] First, as illustrated in FIG. 4A, a coating apparatus 500 is
started and operates by coating a thermosetting adhesive 501 on sides of
the first and second partial masks 110a and 110b that are to be bonded to
each other.

[0062] Here, the sides of the first and second partial masks 110a and 110b
which are to form a bonding portion of the first and second partial masks
110a and 110b are inclined and are parallel to each other. However, the
sides of the first and second partial masks 110a and 110b may also be
vertically parallel as illustrated in FIG. 3G.

[0063] Then the sides of the first and second partial masks 110a and 110b
which are each coated with the thermosetting adhesive 501 are adhered to
each other as illustrated in FIG. 4B. To adhere and align the first and
second partial masks 110a and 110b, a vision camera 200 may be used. For
example, a reference pattern glass may be disposed under the first and
second partial masks 110a and 110b to observe and determine whether
positions of a reference pattern and the first and second partial masks
110a and 110b correspond to each other so as to align the first and
second partial masks 110a and 110b.

[0064] Next, as illustrated in FIG. 4c, the first and second partial masks
110a and 110b are disposed on a base plate 10 and a heat roller 600
including a heater (not shown) therein is brought in direct contact with
the bonding portion to cure the thermosetting adhesive 501.

[0065] That is, as the heat roller 600 rolls along the line of the bonding
portion, the thermosetting adhesive 501 is heated to thereby cure the
thermosetting adhesive 501 and obtain a rigid bonding state.

[0066] After curing the thermosetting adhesive 501 on an upper surface of
the first and second partial masks 110a and 110b and spending a
predetermined stabilization time in the above-described manner, the first
and second partial masks 110a and 110b may be reversed and the same
operation of heating and curing may be performed on a lower surface of
the first and second partial masks 110a and 110b as well, as illustrated
in FIG. 4D.

[0067] That is, the bonding portion on the lower surface of the first and
second partial masks 110a and 110b is heated to cure the thermosetting
adhesive 501.

[0068] Consequently, the thermosetting adhesive 501 coated on the sides of
the bonding portion of the first and second partial masks 110a and 110b
is cured so as to obtain a rigid bonding state, and thus a split mask 110
including the deposition pattern 111 corresponding to a large screen is
manufactured.

[0069] Split masks 110 manufactured in this manner are attached to the
frame 120 to form the mask frame assembly 100 as described above with
reference to FIG. 1.

[0070] Meanwhile, while the heat roller 600 is used to heat and cure the
thermosetting adhesive 501 of the bonding portion in the operations
illustrated in FIGS. 4C and 4D, a blower 700 as illustrated in FIGS. 4E
and 4F that blows hot air 701 to heat the thermosetting adhesive 501
without touching the bonding portion may be used instead.

[0071] That is, referring to FIG. 4E, the blower 700 is used to blow hot
air 701 at the upper surface of the first and second partial masks 110a
and 110b to cure an upper portion of the thermosetting adhesive 501, and
then the first and second partial masks 110a and 110b are reversed to
cure a lower portion of the thermosetting adhesive 501.

[0072] Accordingly, a bonded structure formed of the first and second
partial masks 110a and 110b that are rigidly bonded by using the
thermosetting adhesive 501, that is, the split mask 110, is formed. A
plurality of the split masks 110 manufactured in this manner are attached
to the frame 120 to form the mask frame assembly 100 as described above
with reference to FIG. 1.

[0073] While the upper surface and the lower surface of the first and
second partial masks 110a and 110b are sequentially cured in the
above-described embodiment, the two surfaces may also be cured at the
same time by using a plurality of heat rollers 600 or a plurality of
blowers 700 as illustrated in FIG. 4G or 4H.

[0074] Accordingly, the split masks 110 that include the deposition
pattern 111 corresponding to a large screen may be easily manufactured
using the above-described operations without an increase in the amount of
etching errors.

[0075] In addition, the mask frame assembly 100 for deposition of thin
films according to the embodiments of the present invention may be used
in various deposition operations such as a patterning operation of
organic emissive layers.

[0076] While embodiments of the present invention have been particularly
shown and described, it will be understood by those of ordinary skill in
the art that various changes in form and details may be made therein
without departing from the spirit and scope of the present invention as
defined by the following claims.

Patent applications by Eui-Shin Shin, Yongin-City KR

Patent applications by Jae-Seok Park, Yongin-City KR

Patent applications by Kyu-Bum Kim, Yongin-City KR

Patent applications by Young-Geun Cho, Yongin-City KR

Patent applications by Samsung Mobile Display Co., Ltd.

Patent applications in class WORK SURFACE SHIELDS, MASKS OR PROTECTORS

Patent applications in all subclasses WORK SURFACE SHIELDS, MASKS OR PROTECTORS